Thu Nov 23 16:36:19 EST 2017
* "ps_recv" counts only packets that *passed* the filter,
* not packets that didn't pass the filter. This INCLUDES
* packets later dropped because we ran out of buffer space.
* "ps_drop" counts packets dropped because we ran out of
* buffer space. It doesn't count packets dropped by the
* interface driver. It counts only packets that passed
* the filter.
In Linux it seems ps_recv already contains the number dropped, so adding
ps_drop to them could increase the counter.
At least that's what I am getting from all of this. I am way out of my
depth at this point, and have to admit that I could be totally off base.
--- Original Message ---
From: "snort user" <snortuser at ...125...>
To: snort-users at lists.sourceforge.net
Subject: RE: [Snort-users] 2.1.3rc1 Performance
Date: Wed, 19 May 2004 22:11:50 +0000
I use the .0.8.x branch of lipcap so Im not sure if this applies to
branches but all the following has been verified for this branch.
I actually noticed this a long time ago and a few other bugs maybe I
get on the devel list.
The stats are being reported inaccurately in the util.c file. Heres part
-- code snip --
"Snort analyzed %u out of %u packets, ",
- end snip--
ps_recv is the total packet recevied (meaning recieved and dropped)
ps_drop is the total dropped
So this is an inaccurate reading. The reallly bad thing is that whatever
packet loss it tells you is actually worse since it uses
(packets_dropped/(total_packet+packet_dropped)). Which is increasing the
total packets it thinks its see. So if you seeing 40% packet loss is more
Ive been doing extensive tests with snort lately and ive determined that
even on a linux system with very high perfomance hardware you can really
more than 200 Mb/s without dropping packets unless you really limit your
rules and remove preprocessors such as stream4 and frag2. There really
to be a better pattern matching and optimization for snort to not drop so
Id be interested in hearing any schemes or ideas people have tried for
improving the performance of snort on linux.
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